Refining tall oil



Patented Oct. 17, 1950 REFINING TALL OIL Louis E. Gates and Lee A. Radeker, Canton, N. 0.. assignors to The Champion Paper and Fibre gfllmpany, Hamilton, Ohio, a corporation of No Drawing. Application March 12, 1947,

Serial No. 734,232

6 Claims.

This invention relates to a process of refining tall oil. In particular it relates to a process for producing tall oil having a high fatty acid content and having no objectionable odor.

Although tall oil, obtained as a by-product in the sulfate and soda pulping process, is an inexpensive source of fatty acids and resin acids its use in industry has been limited because of the oflensive odors associated with it, and because it exists as a mixture dimcult to separate into its constituents. It has been proposed to remove odors, reduce the tendency to crystallize, improve the color and otherwise refine tall oil by various methods such as heating, distilling with and without the aid of steam, treating with chemical agents, solvent extraction, treating with adsorbents such as fullers earth, etc., with varying degrees of success. Separation of the resin acid constituents from the fatty acid constituents is much more difilcult and requires involved treatment such as extraction with a selective. solvent, fractional distillation, selective esterification, saponification, and other chemical steps, or combinations of these operations. These separation methods, even when employed in a large number of steps, do not yield a clear cut fraction of fatty acids or resin acids and are relatively expensive for the improvement gained.

One object of this invention is to produce a refined tall oil. Another object is. to improve the odor of tall oil. A further object is to reduce substantially the resin acid content of tall oil to produce a fatty acid material of good commercial value. These and other objects are attained in a relatively simple, economical manner.

We have discovered that the addition of very small amounts of orthophosphoric acid or its acid salts to tall oil followed by heating to a moderate temperature results in marked improvements in the tall oii thus treated. There are at least two definite improvements resulting from this treatment. In the first place the sulfur compounds, which are present in thetall oil in some not very well understood combination, are released much sulfuring. This release ofthe malodorous sulfur specified'is over and above the amount necessary to neutralize any soaps present in the tall oil. Larger amounts of phosphoric acid, of the order of 1% to 2%. afford some improvement over the smaller amounts, but in most cases it is not sumcient to warrant the additional cost. The acid or salt is added before 200 F. is reached and in ei-'- 2o ther case, good agitation is maintained. The

quantity of salt added should be such as to give a (H+) content equivalent to that obtained with from 0.1% to 0.5% of the acid.

The temperature to which the mixture of phosphoric acid and tall oil should be heated is advancompounds is made possibleat temperatures far below those which result in pyroiytic decomposition of the tall oil. In the second place improvement results in that upon cooling of the treated tageously about 300 F. Good results are .obtained at temperatures in the range of about 280- 330 F. If the temperature is carried much above 350 F., there is no advantage to be gained as excessive mechanical and decomposition losses are encountered.

Heating of the tall oil in the presence of phosphoric acid is continued until evolution of sulfides can no longer be detected by smell, reaction of the vapors on paper moistened with lead acetate solution, or other suitable means. The heating is preferably carried out in a vessel which is closed, except for a duct to carry our the vapors evolved, in order to exclude air and thereby prevent formation of pitch and oxidation products.

Although the operation may be carried on by simply heating phosphoric acid and-tall oil to the temperature specified, the removal of the released sulfide bearing gas is facilitated by blowing a non-oxidizing as, for example carbon dioxide,

nitrogen, etc., through the hot mixture. We have i found steam to be particularly advantageous for this purpose. It is possible that the steam. may also exert some chemical, possibly hydrolytic, effect which is advantaseous. Blowing is also beneficial in that it causes the removal of some of the unsaponifiable constituents of tall oil at this point, and certain oily bodies in tall oil that are of foul odor and easily turn dark when exposed to air and/or light.

The rate of introduction of gases is governed by the losses from the tall oil due to entrainment and distillation; such losses, preferably, should be in range of 2-5%. Because of the action of the phosphoric acid, any blowing operation in its presence is much more effective in the removal of undesirable odors than in its absence, permitting a substantial savings in heat and other costs since lower temperatures and shorter blowing times are required and less pyrolytic decomposition occurs. Also, such expedients as reduced pressure during blowing are unnecessary.

After cooling of the treated tall oil the resin acid crystals form easily and rapidly and may be separated mechanically by filtration, centrifuging, etc. Crystals high in resin acid content, that is containing of the order of 80% to 90% of resin acids, are obtained and in amounts equal to between 25% and 30% of the weight of the tall oil. The liquid portion is correspondingly depleted of resin acid and increased in fatty acid content.

It is well known that the separation of the fatty acid from the resin acid content by various distillation methods is very unsatisfactory in obtaining sharp separations. However, by using this filtered product of our process as the starting material in a fractional distillation, a greatly improved separation can be obtained because of the higher ratio of fatty acids to resin acids at the beginning of the operation. Similarly separation of the fatty acids from the resin acids by esterification or selective solvent extraction is more effective when carried out on our improved tall oil than on a crude oil.

The invention is illustrated by the following example:

Crude tall oil, in the amount of 400 lbs., is pumped into stainless steel tank equipped with direct and indirect steam coils, and a recirculating pump. Circulation is started and 2 lbs. of phosphoric acid (85% H3PO4 content) is added directly to the charge. Next the indirect steam coil is turned on and when the temperature of the oil reaches about 220 F. the circulating pump is shut down as the direct steam (125 p. s. i.) is turned on. The temperature of the oil is increased to 300 F. and maintained 120 F. by means of the indirect coil for the remainder of the steam blowing. The vapors arising from the tank are tested periodically with strips of paper which have been dipped in a 10% solution of lead acetate. When a treated strip remains in the vapors for 5 minutes with no appreciable darkening due to formation of lead sulfide all the steam is shut off. Total steaming time is approximately 6 hours. The blown oil has a pleasant, faint, caramel-like odor as compared to the original foul sulfur-compound odor.

The treated oil is allowed to settle for about 2 hours after all heating has been terminated; hard black pitch in an amount equal to 0.5% of the original weight of the oil settles out leaving the hot oil dark red in color but clear and bright in appearance. The tall oil is then pumped through a cooler and delivered to a crystallizing tank and allowed to stand for two days. The product, practically a solidified mass, is forced out of the tank into a basket-type centrifuge by means of compressed air. The liquid portion of the tall oil passes from the centrifuge to a collect- Cry tal Crystals 5 Tan on Free 011 Moisture T Ash 0. 01 Unsaponiflables. 5. 37 0. 1!) Resin Acids 28. 35 83. 06 Fatty Acids (By difference 47. 66. 27 10.63 Acid N o. 169 161 Baponiflcation N o. 177 177 180 The process makes it possible to obtain high yields of resin acids without resorting to the use of refrigeration or other expensive equipment and procedures. Resin acid crystals in the amount of 10% to 15% by weight can be separated from crude tall oil upon prolonged standing, whereas phosphoric acid treated tall oil yields 25% to 30% of resin acid crystals on the weight of the oil.

By the process of this invention tall oil is readily and cheaply freed of foul odors with simple, readily available equipment and a minimum of material and labor cost, and the resin acids of the oil are more easily removed so that a product rich in fatty acids is obtained. The resin acids obtained are suitable for use in varnishes, inks, papermaking size, etc., while the fatty acid-rich, sulfide-free tall oil is adapted for use in soaps, emulsifiers, plasticizers, etc.

We claim:

1. In the process of refining tall oil the steps which comprise adding to the tall oil a material from the group consisting of orthophosphoric acid and its acid salts in an amount equivalent to not more than 0.5% of orthophopsphoric acid on the weight of the tall oil, heating the mixture to a temperature not exceeding about 350-F. and passing a stream of non-oxidizing gas through the mixture.

2. In the process of purifying tall oil, the step which comprises blowing steam through heated tall oil which contains a material selected from the group comprising orthophosphoric acid and its acid salts in an amount equivalent, to from 0.1% to 0.5% of orthophosphoric acid on the weight of the tall oil, the temperature of said heated tall oil not exceeding about 350 F.

3. In the process of purifying tall oil, the steps which comprise adding a material from the group consisting of orthophosphoric acid and its acid salts in an amount equivalent to not more than 0.5 of orthophosphoric acid on the weight of the tall oil, heating the mixture to a temperature between 280 F. and 350 F. and passing steam through the mixture.

4. The process of treating tall oil which comprises adding to the tall oil orthophosphoric acid in an amount equal to between 0.1% to 2% on the tall oil, heating the mixture to temperature between 280 F. and 330 F., passing steam through the mixture until there is no further evolution of sulphide odors, cooling the mixture, and mechanically separating the crystals which form.

5. Process of prcducing a refined tall oil free of objectionable odor which comprises adding from 0.1% to 0.5% of orthophosphoric acid to crude tall 011, heating' the mixture, passing steam through the mixture while it is maintained at a temperature between 280 F. and 330 F. until lead acetate paper fails to give a sulphide test after flve minutes exposure to the vapor eflluent, allowing the mixture to cool, and mechanically separating the precipitated crystals fromthe liquid portion of the mixture.

6. The process of treating tall oil which comprises adding to the tall oil from 0.1% to 2 of tall oil until evolution of sulfide odors ceases, set-' tling out the insoluble materials from the hot tall oil and removing the settlings. cooling the tall oil, and separating from the tall oil the resin acid crystals which form.

LOUIS E. GATES. LEE A. RADEER.

REFERENCES CITED The following references are of record in the tile 0! this patent:

' UNITED STATES PATENTS 2,441,198 Babayan May 11, 1948 

1. IN THE PROCESS OF REGINING TALL OIL THE STEPS WHICH COMPRISE ADDING TO THE TALL OIL A MATERIAL FROM THE GROUP CONSSITING OF ORTHOPHOSPHORIC ACID AND ITS ACID SALTS IN AN AMOUNT EQUIVALENT TO NOT MORE THAN 0.5% OF ORTHOPHOPSPHORIC ACID ON THE WEIGHT OF THE TALL OIL, HEATING THE MIXTURE TO A TEMPERATURE NOT EXCEEDING ABOUT 350*F. AND PASSING A STREAM OF NON-OXIDIZING GAS THROUGH THE MIXTURE. 